From: Robin Murphy <robin.murphy@arm.com>
To: Lu Baolu <baolu.lu@linux.intel.com>, Tom Murphy <tmurphy@arista.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
Ashok Raj <ashok.raj@intel.com>, Dmitry Safonov <dima@arista.com>,
linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
jacob.jun.pan@intel.com, David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH v3 1/8] iommu: Add ops entry for supported default domain type
Date: Thu, 9 May 2019 17:11:42 +0100 [thread overview]
Message-ID: <56205a21-c72f-a460-77a2-4bb4f46f6e08@arm.com> (raw)
In-Reply-To: <3e0da076-4916-1a02-615c-927c1b3528b8@linux.intel.com>
On 09/05/2019 03:30, Lu Baolu wrote:
> Hi Robin,
>
> On 5/7/19 6:28 PM, Robin Murphy wrote:
>> On 06/05/2019 16:32, Tom Murphy via iommu wrote:
>>> The AMD driver already solves this problem and uses the generic
>>> iommu_request_dm_for_dev function. It seems like both drivers have the
>>> same problem and could use the same solution. Is there any reason we
>>> can't have use the same solution for the intel and amd driver?
>>>
>>> Could we just copy the implementation of the AMD driver? It would be
>>> nice to have the same behavior across both drivers especially as we
>>> move to make both drivers use more generic code.
>>
>> TBH I don't think the API really needs to be involved at all here.
>> Drivers can already not provide the requested default domain type if
>> they don't support it, so as long as the driver can ensure that the
>> device ends up with IOMMU or direct DMA ops as appropriate, I don't
>> see any great problem with drivers just returning a passthrough domain
>> when a DMA domain was requested, or vice versa (and logging a message
>> that the requested type was overridden). The only type that we really
>> do have to honour strictly is non-default (i.e. unmanaged) domains.
>
> I agree with you that we only have to honor strictly the non-default
> domains. But domain type saved in iommu_domain is consumed in iommu.c
> and exposed to user through sysfs. It's not clean if the iommu driver
> silently replace the default domain.
Right, I did get a bit ahead of myself there - the implicit step before
that is to fix default domain allocation so that the core actually
passes the relevant device which it has to hand, such that the IOMMU
drivers *can* make the right decision up-front.
Robin.
next prev parent reply other threads:[~2019-05-09 16:11 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-29 2:09 [PATCH v3 0/8] iommu/vt-d: Delegate DMA domain to generic iommu Lu Baolu
2019-04-29 2:09 ` [PATCH v3 1/8] iommu: Add ops entry for supported default domain type Lu Baolu
2019-05-06 15:32 ` Tom Murphy
2019-05-07 10:28 ` Robin Murphy
2019-05-09 2:30 ` Lu Baolu
2019-05-09 16:11 ` Robin Murphy [this message]
2019-05-10 5:29 ` Lu Baolu
2019-05-09 2:22 ` Lu Baolu
2019-04-29 2:09 ` [PATCH v3 2/8] iommu/vt-d: Implement apply_resv_region iommu ops entry Lu Baolu
2019-04-29 2:09 ` [PATCH v3 3/8] iommu/vt-d: Expose ISA direct mapping region via iommu_get_resv_regions Lu Baolu
2019-04-29 2:09 ` [PATCH v3 4/8] iommu/vt-d: Enable DMA remapping after rmrr mapped Lu Baolu
2019-04-29 2:09 ` [PATCH v3 5/8] iommu/vt-d: Implement def_domain_type iommu ops entry Lu Baolu
2019-04-29 20:03 ` Christoph Hellwig
2019-04-30 2:11 ` Lu Baolu
2019-05-06 15:25 ` Tom Murphy
2019-05-09 4:31 ` Lu Baolu
2019-04-29 2:09 ` [PATCH v3 6/8] iommu/vt-d: Allow DMA domains to be allocated by iommu ops Lu Baolu
2019-04-29 2:09 ` [PATCH v3 7/8] iommu/vt-d: Remove lazy allocation of domains Lu Baolu
2019-04-29 2:09 ` [PATCH v3 8/8] iommu/vt-d: Implement is_attach_deferred iommu ops entry Lu Baolu
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